It's all about reasonableness. It is reasonable to assume that if the selector switch has no auto setting that it is semi-auto.

There is no switch whatsoever, let alone a 'full auto' setting...

It is 'reasonable' to assume that by a simple glance at the gun one could verify that there was no switch, thus no need to touch it whatsoever...

What was the 'reasonable' purpose of dry-firing it?

I'd like to add that I have no want or need to walk down the street with a gun slung over my back, but if I were walking to or from coyote hunting with an AR, I do not expect to be stopped and disarmed because someone drove by and called LEO's allegedly because it 'looks' like I am carrying a 'full-auto'...